Essential to the control of acute rheumatic fever and rheumatic heart disease is the proper management of streptococcal upper respiratory tract infection. These sequelae of streptococcal infections remain high on the list as causes of cardiovascular morbidity and mortality. The major objective of this study is to investigate improved methods of diagnosis and control of streptococcal upper respiratory tract infections--while at the same time learning more of the epidemiology of the spread of group A streptococci--as means of ultimately reducing the incidence of rheumatic fever and rheumatic heart disease. The study will be carried out among index cases of pharyngitis and their family contacts seen in a clinic-emergency room setting in an urban area. Clinical observations and both established and new laboratory techniques will be serially obtained and correlated to assist in documenting host and bacterial risk factors affecting the epidemiology of streptococcal infections and in differentiating bona fide streptococcal infection from the carrier state.